The present invention relates generally to an abrasion resistance testing and more specifically to abrasion resistance testing of non-conductive material.
Abrasion testers for testing the abrasion resistance of non-conductive materials, generally including insulative wires is well known. It generally includes securing the wire in a fixture and abrading at the point of abrasion until bare wire is exposed. A contact is made to the covered wire and the abrading tool is generally conductive. Thus, when the wire is exposed at the abrasion point, an electric circuit is completed. Acceptable abrasion resistance can then be determined as a function of the time period between the beginning of the abrasion process and when an electrical contact has been made to the wire at the point of abrasion. This testing process and equipment is described in military Specification MIL-T-5438 (19 Dec. 1949) and Society of Automotive Engineer SAE J1128 (1995).
The use of a piano wire as the abrading material and as a conductor of the sensor circuit is illustrated in U.S. Pat. No. 2,373,115. Moving the wire relative to a knife blade is illustrated in U.S. Pat. Nos. 2,329,062 and 2,372,093. Electrical contact is made by the blade to the interior wire. Applying weight to a blade until it pierces the installation is illustrated in U.S. Pat. No. 3,150,523.
A presently used system, for example, Model CAT-1 from Glowe-Smith Industrial, Inc. is illustrated in FIGS. 1 and 2. The insulative wire 10 includes internal conductors 12 and an insulative layer or insulator 14. An abrading or abrasive strip 20, as illustrated in FIG. 2, includes an abrasive surface 22 with spaced conductive segments 24 thereon. Strip 20 progresses from a supply roll 26 to a point of abrasion, point A, to a take up reel 28. The point of abrasion A is between a guide 30 for the abrasive strip 20 and a weight 32. A controller 40 is electrically connected to the wire conductor 12 by conductor 42 and to a sensing roller 43 on the top surface of abrasive strip 20 adjacent insulative wire 10 through conductor 44. The controller 40 controls a motor that drives the reels 26 and/or 28 and abrade the insulation 14 with the abrasive strip 20 until the wire conductor 12 is exposed at the abrasion point A. This exposure is determined by one of the conductive segments 24 coming into contact with the exposed wire conductors 12.
Since conductive segments 24 are spaced along the length of the abrasive strip, the point at which this contact is made is a function of the spacing of the conductor segments, and therefore is not extremely accurate. Also, the abrasive strip 20 with the conductive strips 24 is a specialty item and increases the cost of the tester. Another problem is that the conductor strips 24 are not of uniform quality. Their ability to make contact on the move would be a function of the spacing and force between the weight 32 and the guide 30 as well as the alignment of the roll. Thus, the results are very unreliable.
Thus, it is an object of the present invention to provide an abrasion tester which provides more accurate results.
Another object of the present invention is to provide an abrasive tester which is capable of using ordinary abrasive strips.
An even further object of the present invention is to provide an abrasive tester which does not require conductive contact with the wire conductor.
These and other objects are achieved by an abrasion tester using an abrasive non-conductive strip moved along the first surface of a non-conductive material to be tested at a point of abrasion to abrade the material to be tested. The dielectric strength of the material to be tested and the abrasive strip at the point of abrasion between a first and second electrode is measured. The abrading process is stopped when a predetermined dielectric strength is measured. Determination is then made of acceptable abrasion resistance of the material to be tested as a function of the initiation and termination of abrading.
The structure includes a fixture for retaining a non-conductive material to be tested. A driver drives the abrasive non-conductive strip along the material to be tested at the point of abrasion. The first and second electrodes are positioned so as to be separated by the material to be tested and the non-conductive abrasive strip. The dielectric strength measuring device is connected to the first and second electrodes. A controller starts the driver and stops the driver when the predetermined dielectric strength is measured. The strip material is a continuance strip fed from a feed spool to a take up spool past the point of abrasion. A conductive guide at the point of abrasion forms one of the electrodes. For the testing of insulative wire, the conductor of the insulative wires is second electrode. The predetermined dielectric strength is a value at which the material to be tested is worn through at the abrasion point. The length of tape used between the initiation and termination of the abrasion is used as an indication of the abrasion resistance. This length is measured or counted. The measuring device applies a voltage across the first and second electrode and measures the leakage current through the non-conductive material and strip therebetween as a measure of the dielectric strength.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.